Although powdered pharmaceutical preparations are enclosed in thin-walled paper pouches or pouches made of plastic film, preparations such as tablets or capsules are enclosed in blister packages referred to as press-though packages (PTP). The preparation can be removed by breaking a sheet-like cover by pressing on the preparation enclosed in the blister package with a finger.
Pharmaceutical preparations are subject to deterioration of the pharmacologically active ingredient following absorption of moisture. Consequently, a desiccant such as silica gel has conventionally been enclosed within the outer pouch that encloses the blister package. However, the work of placing a desiccant in the outer pouch is labor-intensive, and there is also the risk of the desiccant being accidentally swallowed or consumed. In addition, there was also the problem of a low level of humidity being unable to be maintained within the blister package after opening the outer pouch, thereby resulting in progression of deterioration of the pharmaceutical preparation. Moreover, since certain preparations are susceptible to oxidative degradation or emit a peculiar odor, there is also the need to be able to absorb oxygen and odors present within the blister package.
In contrast, Patent Document 1 discloses a technology whereby long-term stability of a pharmaceutical preparation is improved by forming an absorbing layer having an absorbent within a blister package. In this technology, a dome-shaped pocket is first formed in a laminate consisting of a barrier layer in the form of a substrate and an absorbing layer. A pharmaceutical preparation in the form of a tablet is then placed in the pocket and sealed therein by a cover. According to this technology, the maintaining of a dry state, prevention of oxidation and efficient removal of odors are thought to be possible even if a desiccant and the like is not included in the outer pouch.
In addition, since some pharmaceutical preparations are susceptible to ultraviolet light, if a transparent packaging container is used, there is the risk of degradation of the pharmacologically active ingredient. In contrast, Patent Document 2, for example, discloses a so-called aluminum blister package that employs a technology whereby an aluminum layer is also formed in the laminate for a blister package on the top side instead of only in a cover on the back side of the blister package. According to this technology, since an aluminum layer is provided in the blister package, although it is no longer possible to visualize the pharmaceutical contained therein, ultraviolet light can be blocked and barrier properties can be further enhanced.
In an aspect that simply combines the aforementioned two technologies, problems such as rupturing of the roof of the dome or the formation of cracks in the skirt or shoulder of the dome occur when a dome-shaped pocket is formed in a laminate for a blister package. In order to overcome these problems, Patent Document 2 inserts a reinforcing layer using a specific polymer between the aluminum layer and the absorbing layer. In this aspect, although moldability is improved considerably, depending on the type of molding machine or molding depth, there were cases in which the shoulder of the pocket ended up cracking or pinholes formed therein.